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Home Field Advantage II

Posted by Chase Stuart on July 13, 2006

Is there such a thing as a "dome field advantage?" Whenever a dome team has a strong season and happens to be very good at home, sportswriters get to write about the special dome field advantage. Supposedly, it's tougher to win in a dome because of the loud crowd noise, and maybe the artificial turf and the absence of natural elements. So do the facts bear this our? Do dome teams do better than regular teams at home?

According to the data, the answer is no. That's an important caveat, though. The numbers just show one thing: home wins minus road wins, for all teams that played in a dome. It's certainly possible that some special advantage exists for dome teams that wasn't examined in this study. But at the end of this post I'll throw out a theory on why there might actually be a "dome team disadvantage."

Since 1983, eight teams have played in a dome. The Atlanta Falcons (1992-2005), Detroit Lions (1983-2005), Houston Oilers (1983-1996), Indianapolis Colts (1984-2005), Minnesota Vikings (1983-2005), New Orleans Saints (1983-2004), Seattle Seahawks (1983-1999) and the St. Louis Rams (1996-2005).

There was a bit of noise in the data, so I eliminated the '95 Rams and last year's Saints teams. When the Rams relocated to St. Louis in 1995, the Edward Jones Dome wasn't complete. So the Rams first four home games were played at Busch Stadium, and the remainder in the Dome. The Rams went 3-1 at Busch and 1-3 indoors. Due to Hurricane Katrina, the Saints played three games indoors at the Alamodome in San Antonio (1-2), and four home games outdoors at Tiger Stadium in Baton Rouge (0-4) last year. The remaining "home" game was played at Giants Stadium, the star of yesterday's post.

The eight dome teams won 188 games more at home than on the road during the relevant time period, spanning 139 seasons. That comes out to an average of 1.35 more home wins per season.

The Houston Texans (2002-2005) play in Reliant Stadium, which has a retractable roof. I'm not sure which games were played with the roof open and which with the roof closed. The Dallas Cowboys (1983-2005) play at Texas Stadium, which is an open-air stadium -- basically a dome with a hole in the center. I didn't know whether to count either Texas team as a "dome" team or "regular" team, so I just put them in a separate category. Interestingly enough, my classification shouldn't matter: over 26 seasons the two teams won 35 more home games than road games, an average of 1.35 more wins per season.

So how does that compare to the rest of the NFL? The league has increased from 28 to 32 teams since the first year in the study. Over the 22 seasons (remember, the 1987 strike season data were excluded), that amounts to 649 seasons. NFL franchises have won 881 more games at home than on the road, average of 1.36 more wins per season. If you eliminate all the dome teams, the Cowboys and Texans, and the 2005 Saints and 1995 Rams, NFL teams average 1.37 more wins per season at home than on the road.

We have 482 non-dome seasons, and 188 dome seasons. I'm not sure what a "significant" sample size would be, but considering how close the two averages were (1.35 and 1.37), at the least the burden of proof should shift to those who think dome teams have an advantage.

I promised you some theory in addition to the numbers. We've seen that dome teams appear to have the exact same home field advantage as regular teams. I say appear, because all the data show is that dome teams win the same additional number of games (compared to regular teams) at home than on the road. But is it possible that dome teams are actually worse at home but the numbers don't show it?

Isn't the general feeling that dome teams aren't as good on the road because they're not used to the conditions? This would artificially inflate a dome team's rating under my current system, because a team grades better at home the worse it does on the road. If dome teams actually perform poorly on the road -- as we might expect -- then the HFA of dome teams should should be greater than the league average, if dome teams are equally strong at home. This leads us to one of three conclusions:

  • Dome teams are actually weaker at home; they just look equal because they have trouble winning on the road.
  • Dome teams actually aren't weaker at all on the road; it just seems that way because we hear it all the time. The flipside of all the above numbers is that dome teams only lose 1.35 less games on the road than at home each year.
  • Something else. Maybe it's a small sample size. Maybe dome teams are below average at home when they're bad, but above average at home when they're good. Maybe schedule somehow factors in here. Maybe there's some other force driving the numbers that I haven't isolated. Who knows.

There's also the argument that dome teams are still actually better at home, but the numbers don't show it. Let's take a quick look at a few case studies. We'll use HFA rating as a shorthand for home wins minus road wins.

Atlanta's HFA rating was 9.5 during the 8 years the Falcons played at Fulton County Stadium; playing indoors the last 14 seasons, Atlanta's won 22.5 more games at home. The Houston Oilers' HFA was 21 in thirteen seasons at the Astrodome; the Titan's HFA rating was 9 in 9 years. But on the other hand, the Seahawks won just 23 more home games than road games in sixteen seasons in the Kingdome. Since moving to Qwest Field, Seattle's HFA is 12 in six years.

Here's an interesting one. From 1983-1994, the Raiders and Rams both won 9 more games when playing in Los Angeles than when on the road. The Raiders moved to Oakland and despite the notoriety of Raider Nation and the Black Hole, have an HFA of only 11 in 11 years. The Rams, in ten season indoors, won 15 more at home.

If there's such a thing as a Dome Field Advantage, it's certainly hard to quantify it. My guess is that when teams like the '98 Vikings, '99 Rams or the '05 Colts have a dominant offense and look unstoppable at home, it's a nice story to think it's the dome that helps. But in general, great teams almost always look pretty good, and usually look unbeatable at home no matter where they play. The same people that talk up how hard it is to play against a dome team because of the noise, probably mention how difficult it is to win in the cold against the Packers, Broncos and Chiefs. Even teams with no special weather advantage -- warm weather teams like Arizona, Tampa Bay and Dallas -- have above average HFA factors.

We know that over the last 22 years, home teams have won 58.5% of all games. I'll end with a breakdown of HFA separated out by total team wins.

Wins	HFA	Teams	HFA/Teams
1 -4 6 -0.67
2 12 14 0.86
3 29 25 1.16
4 48 44 1.09
5 76 54 1.41
6 94 60 1.57
7 79 69 1.14
8 112 70 1.60
9 121 77 1.57
10 94 73 1.29
11 79 55 1.44
12 66 43 1.53
13 46 22 2.09
14 4 15 0.27
15 2 4 0.50

3.5 -1.5 1 -1.50
4.5 5.5 3 1.83
5.5 -0.5 1 -0.50
6.5 9.5 3 3.17
7.5 -2.5 1 -2.50
8.5 7 4 1.75
9.5 2 2 1.00
10.5 3.5 3 1.17
Totals 881 649 1.36